One of the most exciting things about genetic research is how much it has taught us about the diversity of life on Earth. Case in point: the as-yet-unnamed frog species pictured here. It looks so much like New York City's other leopard frogs that scientists overlooked it for years, but by examining its DNA, researchers have shown that this little creature is actually an entirely new species.

So here's a question: if this new frog looked so similar to all the other leopard frog species in the area (of which there are more than a dozen), how did scientists even think to compare its DNA against all the others' in the first place? Simple: a very attentive PhD student noticed this new leopard frog had a distinctive croak.

"When I first heard these frogs calling, it was so different, I knew something was very off," explained researcher Jeremy Feinberg. He says the new frog is what biologists call a cryptic species, "one hidden within another because we can't tell them apart on sight."

Fortunately, we can tell them apart with our ears. And with nuclear and mitochondrial genetic analysis. You know, just to be sure.